In a general gas circuit breaker, it is necessary to use a material having both high electrical insulating properties and high mechanical strength for an insulating operation rod that supports or drives a puffer blocking unit. As an insulating material, a resin material has better electrical insulating properties. However, a required mechanical strength cannot be sufficiently obtained from this resin material alone. Therefore, as a material for the insulating operation rod, fiber reinforced plastic (FRP), obtained by soaking fibers in resin, is generally used. Among various kinds of fiber reinforced plastic, glass fiber reinforced plastic (GFRP) is frequently used for the insulating operation rod, particularly because GFRP has better manufacturability and workability.
When SF6 gas is decomposed by an arc generated at the time of blocking an electric current, active SF4 gas is generated. This SF4 gas reacts with water in a hermetically-sealed tank, and is hydrolyzed to SOF4 gas and HF gas. Glass fibers in a GFRP insulating operation rod are damaged by decomposition gas such as this HF gas. There is a possible reduction in mechanical strength of the glass fibers in this insulating operation rod. Further, it is known that the surface resistance of the insulating operation rod is reduced by an influence of a conductive substance generated by a reaction of the glass fibers with the decomposition gas, and this eventually leads to creeping destruction of the insulating operation rod.
In a conventional technique disclosed in Patent Literature 1 as a method for solving these problems, a GFRP surface is coated by a coating having a high resistance to decomposition gas (a decomposition-gas resistant coating) to prevent a reduction in mechanical strength and electrical insulating properties of glass fibers.